The present invention refers to an electro-thermal actuator device.
Devices of the indicated type, also known as thermal actuators, usually comprise a casing, for instance made of thermoplastic material, within which there are contained a thermal head and, at least partly, an actuating shaft.
The head comprises a body made of an electrically and thermally conductive material (such as steel), containing a thermally expansible material (such as a wax) within which a piston is at least partially dipped; said body is in contact with an electric heater, typically a PTC resistor, electrically supplied through two terminals.
In some instances, thermal actuators of the above type suffer malfunctions, due to the attack operated by external agents being present in the air.
From document WO9832141 a thermal actuator of the indicated type is known, whose casing is filled with material apt to insulate from the environment components being subjected to electric voltage.
Said material is capable of reticulating so as to form an elastic and compressible foam, i.e. having a reduced mechanical strength to tearing. In this way, following the first operating cycle of the thermal actuator, the portion of the insulating material coating the movable components of the thermal actuator can tear, whereas the remaining portion of the insulating material within the casing remains unbroken, so as to coat the fixed electric components, and protect them from the potentially harmful agents being present in the ambient air.